1. Field of the Invention
The present invention relates to a method of controlling exposure in a film scanner. More particularly, the present invention relates to a method of controlling exposure in a film scanner which captures an image on a developed negative film.
2. Description of the Related Art
The well-known conventional film image capturing apparatus, which is disclosed by WO 90/04301, Japanese Patent Application Laid-open No. 5-75922, etc. , picks up a developed still photographic film by an image sensor such as a charge coupled device (CCD), converts an image into an image signal, and outputs the signal to a TV monitor, which displays a film image. This type of film scanner controls the exposure by a mechanical diaphragm.
Japanese Patent Application No. 6-101189 discloses a method of controlling the exposure in the film scanner, which controls, before capturing a frame image, the exposure time of the line sensor and the gain of each of analog amplifiers in accordance with the R, G and B output voltages which are output from the line sensor when a negative base (the part which has not been exposed at all) on the film is captured.
There is a problem in that no part is secured as the negative base on the developed film. In order to control the exposure by an electronic shutter of the line sensor as stated above, a calibration in accordance with the R, G and B output voltages of the proper negative base is required. In this case, it is very important to determine how to capture the best area representative of the negative base on the film.